code: def test_fixed_words(self):
      text = "tôi không biết"
      fixed_words = ["không biết"]
      actual = word_tokenize(text, fixed_words=fixed_words)
      expected = ["tôi", "không biết"]
      self.assertEqual(expected, actual)
  
file_path: underthesea/tests/pipeline/word_tokenize/test_word_tokenize.py
imports: from unittest import TestCase
  from underthesea import word_tokenize
  import signal
label_desc: Use image node_id 10 for calling the TestWordTokenize obj's underlying member method code with example usage: obj.test_fixed_words() without return types